[jira] [Commented] (OAK-2105) Review padding for blobs collection

["Marcel Reutegger (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-2105?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14138629#comment-14138629 ] 

Marcel Reutegger commented on OAK-2105:
---------------------------------------

Added a function to the oak-mongo.js to get more detailed stats about the blobs collection. Running the tool on a DB where Oak stored about 600k nodes with some binaries of various sizes and with a lucene fulltext index shows a data size of roughly 2GB and a BSON size of 1GB. 

> Review padding for blobs collection
> -----------------------------------
>
>                 Key: OAK-2105
>                 URL: https://issues.apache.org/jira/browse/OAK-2105
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>          Components: core, mongomk
>            Reporter: Marcel Reutegger
>            Priority: Minor
>
> MongoDB does some default padding when it stores documents. The default
> policy adds some padding and then rounds up to the next power of 2 number
> of bytes. For the blobs collection with documents that are written once
> and never modified, this default behavior may not be optimal. E.g. the
> Oak lucene directory implementation splits data into 32k chunks and stores
> them as multi-valued binary properties. This leads to documents that are
> slightly over 32k bytes in size and MongoDB will allocate 64k for it.
> Half of the space is wasted.



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